In this paper, the thermal performance of three different models includes novel torsion step-pitch step, three-bladed spiral tube-triple turbinate tube (TTT), and elliptical spiral tube-oval turbinate tube-elliptical helical tube (TOT) are investigated. Through comparing different turbulence models (RNG k-ε, realizable k-ε, RSM, standard k-ω, and SST k-ω) with the experimental value, the SST k-ω model with high precision is selected to estimate Nusselt number and friction coefficient in a triple spiral tube a uniform torsion step. In this model, the maximum error between numerical and experimental results are 2.7% and 4.7%, respectively. This comparison focused on the tube's thermal performance for heat exchangers; therefore, Nusselt number, pressure drop, and PEC number are considered as critical factors for analyses. The results show that the variable twist spiral tube dramatically enhances thermal performance compared to other cases. The study also confirmed that a constant pitch step in the helical tube has better performance than a variable pitch step.

在本文中，研究了三种不同模型的热性能，包括新型扭转阶跃阶跃、三叶片螺旋管-三重鼻甲管（TTT）和椭圆螺旋管-椭圆形鼻甲管-椭圆螺旋管（TOT）。通过将不同湍流模型（RNG k-ε、realizable k-ε、RSM、标准k-ω和SST k-ω）与实验值进行比较，选择精度较高的SST k-ω模型来估计努塞尔数和三重螺旋管中的摩​​擦系数均匀的扭转步骤。在该模型中，数值和实验结果之间的最大误差分别为 2.7% 和 4.7%。这种比较集中在换热器管的热性能上；因此，努塞尔数、压降和 PEC 数被认为是分析的关键因素。结果表明，与其他情况相比，可变扭曲螺旋管显着提高了热性能。该研究还证实，螺旋管中的恒定螺距步进比可变螺距步进具有更好的性能。